1. Field of the Invention
The present invention relates to a device for automaticaly opening and closing a hinged door, the device having an ability to allow the door to be manually openable in emergency.
2. Description of the Prior Art
Automatic hinged doors are installed in entrances and exits of many buildings. As is well known, a device for automatically opening and closing such a hinged door has a mechanism both for allowing the door to be manually opened in a direction opposite to the direction in which the door is normally opened for permitting occupants to escape in case of emergency such as a fire or an earthquake, and for automatically returning the door to the closed position under the resiliency of a spring which has stored energy when the door is opened, after the occupants have passed through the entrance or exit.
One representative prior art of the above mechanism is disclosed in U.S. Pat. No. 4,333,270. The disclosed mechanism will hereinafter be described with reference to FIG. 6 of the accompanying drawings.
The device for automatically opening and closing the automatic hinged door is installed above an entrance or exit of a building in which the hinged door is mounted. The device has a frame body 15 accommodating a support frame 40 in which there is disposed a rack 42 movable horizontally (as shown in FIG. 6) by a guide rail 41. The rack 42 is held in mesh with a pinion 43 fixed to an operating shaft 3 which can be driven to rotate about its own axis by a motor, not shown. A tubular body 44 has one end coupled by a first sleeve 45 to an end of the support frame 40. A rod 49 is disposed in the tubular body 44 and threaded at one end in the rack 42 for movement therewith. A second sleeve 46 and a spring seat flange 47 are fitted over one end portion of the rod 49. A hollow rod 48 has an end fixedly fitted over an opposite end of the rod 49. The hollow rod 48 is also fitted over an end portion of a smaller rod 51 which extends into the tubular body 44, the smaller rod 51 having an opposite end portion secured to a cover 50 mounted on an opposite end of the tubular body 44. A spring seat flange 54 is fitted over the hollow rod 48 and is held in abutment against a nut 52 threaded over the end of the hollow rod 48 remote from the rod 49 and a third sleeve 53 with one end thereof held in intimate contact with the cover 50. A spring 55 is disposed around the rod 49 and the hollow rod 48 and extends axially between the spring seat flanges 47, 54 for normally urging the spring seat flanges 47, 54 to move them away from each other.
Operation of the prior device thus constructed will be described below. When a power supply switch for the motor is turned on in response to an OPEN command from a control unit (not shown), a door shaft (not shown) coupled directly or via a transmission device to the operating shaft 3 is rotated with the operating shaft 3 in the direction of the arrow A. At the same time, the pinion 43 fixed to the operating shaft 3 is also rotated in the same direction. The rack 42 meshing with the pinion 43 and the rod 49 coupled to the rack 42 are moved to the left in the direction of the arrow A'. Since the spring seat flange 54 fixed to the rod 49 is moved toward the other spring seat flange 47 on the movement of the rod 49, the spring 55 disposed around the rod 49 between the spring seat flanges 45, 54 is compressed. When the motor power supply switch is turned off in response to a CLOSE command from the control unit, the motor is made free to rotate, and the rod 49 is moved to the right in the direction of the arrow B' under the repulsive force of the compressed spring 55. The pinion 43 meshing with the rack 42 and the operating shaft 3 are rotated in the direction of the arrow B for thereby automatically closing the hinged door.
In case of emergency such as a fire or an earthquake, the hinged door should manually be pushed open by rotating the operating shaft 3 in the direction of the arrow B which is opposite to the direction of the arrow A. As the operating shaft 3 rotates in the direction of the arrow B, the rack 42 is moved to the right in the direction of the arrow B', so that the rod 49 connected to the rack 42 is also moved to the right. As a consequence, the spring seat flanges 47, 54 are moved relatively toward each other to compress the spring 55. When the hinged door is released of a manual push after the occupants have passed through the entrance or exit, the rod 49 is moved to the left in the direction of the arrow A' under the force of the spring 55. The pinion 43 in mesh with the rack 42 and the operating shaft 3 are rotated in the direction of the arrow B to close the hinged door automatically.
Automatic hinged doors are generally installed in entrances and exits of buildings and rooms. Any hinged door installed in an entrance or exit of a building is subjected to an external wind pressure. The device for automatically opening and closing such hinged door has to incorporate a spring having a relatively strong spring force in order to prevent the door from vibrating due to the wind pressure. The force with which the hinged door is swung open by the motor while compressing the spring is equal to the force with which the hinged door is manually pushed open while compressing the spring. As a result, in an emergency, the hinged door has to be opened with a manual force strong enough to overcome the relatively strong spring force. However, it is preferable from the standpoint of safety that the manual force required to open the door in emergency be as small as possible, requiring a smaller spring force. This requirement is contradictory to the spring force which should be large enough to withstand wind pressures to which the hinged door is normally subjected.